Long before the first pencil and paper, some curious person drew a triangle in the sand and bisected the three angles. He noted that the bisectors met in a single point and decided to repeat the experiment on an extremely obtuse triangle. Again, the bisectors concurred. Astonished, the person drew yet a third triangle, and the same thing happened yet again!Unlike squares and circles, triangles have many centers. The ancient Greeks found four: incenter, centroid, circumcenter, and orthocenter. A fifth center, found much later, is the Fermat point. Thereafter, points now called nine-point center, symmedian point, Gergonne point, and Feuerbach point, to name a few, were added to the literature. In the 1980s, it was noticed that these special points share some general properties that now form the basis for a formal definition of triangle centerThe Encyclopedia of Triangle Centers lists many centers, but without pictures. The purpose of this page is to introduce a collection of individual pictures, showing constructions of selected triangle centers. The selections are in two groups: Recent Triangle Centers and Classical Triangle Centers.

## Recent Triangle Centers

Schiffler Point

Exeter Point

Parry Point

Congruent Isoscelizers Point

Yff Center of Congruence

Isoperimetric Point and Equal Detour Point

Ajima-Malfatti Points

Apollonius Point

Morley Centers

Hofstadter Points

Equal Parallelians Point

Bailey Point

Gossard Perspector

## Classical Triangle Centers

Centroid

Incenter

Circumcenter

Orthocenter

Fermat Point

Nine-point center

Symmedian point

Gergonne point

Nagel point

Mittenpunkt

Spieker center

Feuerbach point

Isodynamic points

Napoleon points

Steiner point

In addition to triangle centers, there are many interesting centrallines,too. The most famous is the Euler line.

Encyclopedia of Triangle Centers - ETC

Biographical Sketches of Triangle Geometers

A Book about Triangle Centers and Central Triangles:TCCT

Clark Kimberling Home Page